The process of fracking, also known as induced hydraulic fracturing, involves mixing sand and chemicals in water to form a frac fluid and injecting the frac fluid at a high pressure into a wellbore. Small fractures are formed, allowing fluids, such as gas, petroleum, and brine water, to migrate into the wellbore for harvesting. Once the pressure is removed to equilibrium, the sand or other particle holds the fractures open. Fracking is a type of well stimulation, whereby the fluid removal is enhanced, and well productivity is increased.
Multi stage hydraulic fracturing is an advancement to harvest fluids along a single wellbore or fracturing ring. The fracturing string, vertical or horizontal, passes through different geological zones. Some zones do not require harvesting because the natural resources are not located in those zones. These zones can be isolated so that there is no fracking action in these empty zones. Other zones have the natural resources, and the portions of the fracturing string in these zones are used to harvest from these productive zones.
In a multi-stage fracturing process, instead of alternating between drilling deeper and fracking, a system of frac sleeves (e.g. ball-drop) and packers are installed within a wellbore to form the fracturing string. The sleeves and packers are positioned within zones of the wellbore. Fracking can be performed in stages by selectively activating sleeves and packers, isolating particular zones. Each target zone can be fracked stage by stage without the interruption of drilling more between stages.
What are needed in the art are improved apparatus, systems, and methods for fracturing multi-stage zones.